Method for intracorporeal lithotripsy fragmentation and apparatus for its implementation

ABSTRACT

Electro-impulse intracorporeal lithotripsy comprises bringing electrodes of a probe in immediate electrical contact with the calculus and supplying to the electrodes of very short high voltage impulses capable to ignite electrical spark discharge and establish a discharge channel within the bulk of the calculus. The channel goes through the calculus and creates tensile stresses, destroying the calculus.

FIELD OF THE INVENTION

[0001] The present invention relates to lithotripsy fragmentation ofstones, appearing in a human body and in particular to so-calledintracorporeal lithotripsy, during which fragmentation is caused byoperation of the lithotriptor working element within the body. Thepresent invention refers also to an apparatus for fragmentation,disintegrating or otherwise destroying the stones, e.g. gallstones,kidney stones, cystine stones and other calculi, appearing in thebiliary or urinary system of a human body.

[0002] It should be understood however that the present invention is notlimited to the fragmentation of calculi, appearing in the human body. Itcan be also employed for lithotripsy treatment of animals as well.

[0003] Furthermore the present invention is not limited to destroying ofcalculi appearing in merely biliary or urinary systems. It is suitablefor fragmentation of any foreign objects, which might appear in otherlocations of the body, e.g. in blood vessels etc.

BACKGROUND OF THE INVENTION

[0004] Shock-wave lithotripsy stone fragmentation treatment employshigh-energy shock waves to fragment and disintegrate calculi and it canbe broadly categorized according to the pattern of energy transfer tothe calculi. In this connection lithotripsy can be classified asextracorporeal and intracorporeal. The comprehensive overview of variouslithotripsy methods can be found in various sources, e.g. in theInternet site http://www.dsci.com. In accordance with the acceptabledefinitions shock-wave extracorporeal lithotripsy is a process, whichtransfers energy needed for stone fragmentation in the form of shockwaves from an outside source through body tissue to the calculi.Extracorporeal shock wave lithotripsy (ESWL) has proven effective inachieving stone fragmentation. However, since the energy wavetransmission is indirect, and in order to carry out the treatmentsuccessfully it is required precise directional focusing of the energyat the stone through intervening body tissue. This might be associatedwith damaging of the intervening tissues and therefore additionaltreatments might be required to take care of the damage.

[0005] Intracorporeal lithotripsy utilizes a probe advanced with the aimof endoscope and positioned in proximity to the calculus. The energy,required for fragmentation is transferred through the probe to thecalculus and the treatment process is visualized during fragmentation.The mode of energy transfer may be different and accordingly theintracorporeal lithotripsy techniques are divided into following groups:ultrasonic, laser, electro-hydraulic and mechanic/ballistic impact.

[0006] The last group comprises, for example, detonating an explosivenear the stone and causing the shock wave generated by the explosion toact directly upon the stone and crush it into pieces. An example of suchtechnique is disclosed in U.S. Pat. No. 4,605,003, referring to alithotriptor comprising an inner tube inserted within an outer slendertube and provided with an explosive layer or a gas-generating layer. Bythe blasting of the explosive layer or the gas-generating layer, theouter slender tube or the inner tube is caused to collide with the stoneand crush it.

[0007] An example of mechanical impact technique can be found in U.S.Pat. No. 5,448,363 in which is disclosed an endoscopic lithotriptorprovided with a hammer element to periodically strike the stone. Thehammer element is pneumatically driven by a linear jet of air causing itto swing through an arc about a pivot to impact an anvil.

[0008] There are known also many other patents, disclosinglithotriptors, which operation is based on mechanic/ballistic principle,e.g. U.S. Pat. No. 5,722,980, U.S. Pat. No. 6,261,298.

[0009] An example of laser technique is described in U.S. Pat. No.4,308,905, concerning multi-purpose lithotriptor, equipped with laserlight-conducting fibers, through which the energy required for crushingthe stone is conducted.

[0010] Ultrasonic technique is relatively popular and because of itssafety and usefulness is widely accepted. According to this principleultrasound probe emits high-frequency ultrasonic energy that has adisruption effect upon direct exposure to the stone. Direct contact ofthe probe tip and stone is essential for effectiveness of ultrasoniclithotripsy. This technique is implemented in many lithotriptors, e.g.as described in U.S. Pat. No. 6,149,656.

[0011] The most relevant to the present invention is electro-hydraulictechnique, which utilizes electric discharge, ignited between twoelectrodes disposed within the probe and producing shock wave, expandingtowards the calculus through liquid phase, which surrounds the calculus.In the literature electro-hydraulic lithotripsy is defined as the oldestform of “power” lithotripsy. The electro-hydraulic lithotriptor releaseshigh-energy impulse discharges from an electrode at the tip of aflexible probe, which is placed next to the stone. It is considered ashighly effective means of bladder stone shattering and has become anaccepted practice for this use. Since the generated duringelectro-hydraulic lithotripsy treatment shock waves are of sufficientforce the probe must not be used 5 mm or closer to soft tissuesotherwise severe damage will result.

[0012] Since the discharge takes place within liquid phase the calculusis destroyed by virtue of combination of energy of the shock wave,caused by the discharge, hydraulic pressure of the surrounding liquidand collision of fragments in the liquid flow. Below are listed somereferences, referring to intracorporeal lithotripting devices, utilizingthe electro-hydraulic principle.

[0013] A typical electro-hydraulic lithotriptor is described in CA2104414. This apparatus is intended for fracturing deposits such asurinary and biliary calculi as well as arteriosclerotic plaque in thebody. The lithotriptor comprises a flexible elongated guide memberadapted for insertion within the body, means for supplying a workingfluid, a hollow tube mounted on the distal end of the probe, means forinitiating an electric spark within the hollow tube from an externalenergy source, capable of generating pulsed shock waves in the workingfluid for impinging the stone and a nozzle, which is made of shock andheat resistant material and mounted on the distal end of the guidemember. The nozzle is capable of directing the shock waves to a focalpoint for impinging the stone. The lithotriptor is provided also withoptical viewing system.

[0014] In U.S. Pat. No. 2,559,227 is disclosed an apparatus forgenerating shock. The apparatus comprises a truncated ellipsoidalreflector for reflecting the shock waves and a cavity constituting achamber for reflecting said shock waves. The cavity has the sametruncated ellipsoidal shape, while one of the two focal points of theellipsoid being disposed in the cavity opposite the truncated part. Thecavity is filled with a liquid for transmitting the shock waves, forexample oil. The apparatus is provided with a shock wave generatordevice, conventionally comprising two electrodes disposed at leastpartly inside said cavity. The two electrodes are arranged to generatean electric arc discharge at the focal point located in the cavityopposite the truncated part. The apparatus has also means forselectively and instantaneously delivering an electric voltage to saidtwo electrodes provoking electric arc discharge between said electrodesthus generating shock waves propagating through the liquid contained inthe cavity. The electrodes are made of highly conductive material suchas copper or brass and are mounted on an insulator with possibility foradjusting the spacing therebetween.

[0015] In DE 19609019 is described an impact probe, provided with atleast one electrode guided in the tube. The electrode acts on the objectwhen the probe is longitudinally moved in the direction of the objecte.g. a stone. Electro-hydraulic pressure wave is produced at the freeend of the probe.

[0016] It should be stressed that since the probe in conventionalelectro-hydraulic lithotriptors is not in physical contact with thecalculus many efforts are undertaken to focus the maximum of dischargeenergy immediate on the calculus. An example of such an attempt iselectro-hydraulic lithotriptor, known under the trade name THE AUTHOLITHand manufactured by Northgate Technologies. It should be noted, however,in this lithotriptor the energy of shock wave still is transferred via alayer of liquid, remaining between the discharge gap of the probe andthe calculi.

[0017] The efficiency of electro-hydraulic lithotriptor in terms of itsability to fragment a calculus depends on voltage and duration ofelectrical pulses, required for achieving breakdown and initiating thespark discharge, since these parameters are interrelated with the amountof energy, which can be produced by the lithotriptor. Commerciallyavailable electro-hydarulic lithotriptors, e.g. lithotriptor RIVOLITH2280 manufactured by Richard Wolf, are provided with pulse generators,capable to generate pulses with pulse rise time of about hundredsnanoseconds and pulse duration of about hundreds of microseconds.

[0018] It can be easily appreciated that since the energy is transferrednot immediate to the calculus but via a liquid medium, the amount ofenergy required for fragmentation should be sufficient to overcome thestrength of the calculi and to cause its failure after the energy hasbeen delivered through the working liquid (water or urea or physiologicsolution). Electric pulses having duration parameters of commerciallyavailable lithotriptors allow producing rather high energies of about2.5-3 joule, which is sufficient for producing stresses capable tofragment various calculi, appearing in the human body.

[0019] Unfortunately, release of such high levels of energy by producingshock waves might be harmful to the adjacent tissues and thereforepotentially dangerous for the patient.

[0020] The further disadvantage of the known in the artelectro-hydraulic lithotriptors is associated with their inability todetect and monitor the onset of fragmentation. Since the pulse generatorcontinues to generate pulses after the calculus has been alreadyfragmented, unnecessary energy is produced and its release unnecessaryendangers the patient.

[0021] Still further drawback of the electro-hydraulic lithotriptors isassociated with the necessity to have numerous electric discharges whenit is required to destroy especially large and dense calculus. Since thedischarge takes place on the surface of the probe insulation, itdeteriorates the insulation of the probe tip and may cause its failureeven before the treatment session is completed.

[0022] Still another problem of almost all intracorporeal lithotriptorsthat are intended for destroying renal calculi by bringing mechanicalenergy of impact or shock wave is the fact that the stone is usually“displaced” with each pulse of energy, leaving the previous place andbeing “thrown” to another one. This renders the operation complicate andmay cause mechanical damage to the surrounding tissue. Physical“anchoring” of the treated stone would be desirable here.

[0023] An attempt to solve this problem and to extend service life ofthe probe and at the same time to improve treatment efficiency withoutrise of harm to the patient is disclosed in DE 3927260. In this patentis described a probe for electrohydraulic lithotripsy, which is providedwith a head made of impact-resistant ceramic in the form of a roundbass-rod. The rod has two longitudinal channels into which leads areinserted and anchored by a resin material, the ends of the leads beingflush with the end face of the rod. Leads pass to a plug via a flexiblehose, which extends over the head.

[0024] Nevertheless, this particular solution is not designed forimmediate physical contact between the probe tip producing a shockwaveand the calculus.

[0025] There are known lithotriptors, in which such “anchoring” ispossible, e.g. a combined holding and lithotripsy instrument, disclosedin DE 19810696. This combined instrument consists of a highly elasticNiTi alloy and has at least three holding arms, which in their unflexedstate are curved in a tulip-like manner. The end of each holding arm istoothed and bent towards the instrument axis. When the holding arms aredrawn into the instrument tube or working channel they positionthemselves on the calculus and grasp it when they are drawn in evenfurther. The holding device is configured around the instrument axis insuch a way that the angle between directly adjacent holding arms isnever equal to or greater than 180 DEG C. This ensures secure holdingand grasping and thus prevents the grasped calculus from escapingsideways. The securely held calculus can then be fully fragmented tofragments of a predetermined size using the lithotriptor, i.e. eithermechano-ballistically, or by ultrasound, cryogenically or thermally withlaser light.

[0026] Unfortunately this construction is not suitable forelectro-hydraulic mode of operation since the probe tip is not designedto carry electrodes provided with electric insulation and is nottherefore capable of producing shock waves, caused by electricaldischarge.

[0027] On the other hand there is known for some time a method ofso-called high-power electro-impulse destruction of materials, which isbased on the fact that applying of electrical impulses with the risetime of not more than 500 nanoseconds to two electrodes positioned on asolid mineral material immersed in water is associated with producingdischarge, which does not propagate through the surrounding liquidmedium, but rather through the bulk of the solid body. This technologywas developed in late fifties in Russia and since then it has beensuccessfully implemented in such fields like crushing and disintegrationof hard rocks and ores in mining industry, destructing of concreteblocks in building industry, drilling of frozen ground and extremelyhard rocks, crushing of various inorganic materials, etc.

[0028] A survey of this technology can be found in a monograph “Basicsof electro-impulse destroying of materials”, by Semkin et al.,Sanct-Petersburg, Nauka, 1993.

[0029] According to this technology two or more electrodes are placedimmediate on the surface of a solid body (rock) and very short impulsesof voltage U(t) are sent through them. Once an electrical breakdownbetween the electrodes is initiated, it occurs in the bulk of the solidbody and is associated with producing of the breakdown discharge channelthat extends within the bulk of the body. The body itself serves as amedium to promote propagation of the electrical breakdown rather thanthe surrounding medium. Extension of the discharge channel through thebody is accompanied by mechanical stresses, which stretch the body anddestroy it as soon as the tensile strength of the body is exceeded. Infact in the process of electro-impulse destroying the initiation andpropagation of the discharge is similar to a micro explosion within thebody. It can be readily appreciated that since tensile strength of arock is at least an order of magnitude less than its compressivestrength, the electro-impulse crushing is associated with consumption ofmuch less energy, than conventional electro-hydraulic crushing.

[0030] It has been also empirically established, that the probability ofpropagation of the breakdown channel through the body is higher when avery short voltage impulses are applied to electrodes, positioned on asolid body immersed in a liquid medium, since the voltage required forthe breakdown within the bulk of the body is less, than the voltagerequired for breakdown within the liquid medium outside of the body.

[0031] Unfortunately despite the fact that this technology exists formore than 40 years it still has been employed mainly in mining andbuilding industry for destruction of very large objects like rocks orconcrete blocks.

[0032] An example of this application is disclosed in WO 9710058, inwhich is described method of comminuting and crushing solids, forexample, blocks of reinforced concrete. In accordance with this methodthe solid is exploded as a result of shock waves being produced therein.

[0033] Unfortunately the obvious benefits of this technology associatedwith more efficient destruction were never considered for employing insuch completely new application, like medicine in general andintracorporeal lithotripsy in particular.

[0034] In conclusion it should be emphasized that despite the fact thatnumerous lithotriptors have been devised there is still a need for a newapproach that will ensure efficient, reliable, easy and safefragmentation of calculi during intracorporeal lithotripsy.

OBJECT OF THE INVENTION

[0035] The main object of the present invention is to provide a new andimproved method and device for intracorporeal lithotripsy enabling toreduce sufficiently or overcome the above-mentioned drawbacks of theknown in the art solutions.

[0036] In particular the first object of the invention is to provide anew and improved method and apparatus for intracorporeal lithotripsy,ensuring applying tensile stresses to calculi, appearing in the livingbody, instead of compressive stresses.

[0037] Still further object of the invention is to provide a new andimproved method and apparatus for intracorporeal lithotripsy treatmentenabling to reduce probability for traumatizing of adjacent body tissuesduring the treatment.

[0038] Another object of the invention is to provide improved method andapparatus for intracorporeal lithotripsy enabling to detect the onset ofthe fragmentation process and to terminate further generation of highvoltage pulses.

[0039] Still further object of the invention is to provide improvedmethod and apparatus for intracorporeal lithotripsy enabling easy andfast fragmentation and at the same time reliable grasping andcontainment of the calculus being destroyed during the treatment.

[0040] The above and other objects and advantages of the presentinvention can be achieved in accordance with the following combinationof its essential features, referring to different embodiments thereof asa method for intracorporeal lithotripsy and as an apparatus forimplementation of the method.

[0041] According to the embodiment of the invention, which refers to themethod it comprises bringing a probe to the calculus to be fragmented,said probe is provided with electrodes, connected to a means forgenerating of high voltage impulses, said impulses are supplied to theelectrodes for igniting spark discharge between them and release ofenergy, causing fragmenting of the calculus, wherein the methodcomprises bringing of at least one of the electrodes in electricalcontact immediate with the calculus so as to establish a dischargechannel capable to create shock waves and stresses, which excess thestrength of the calculus material.

[0042] The embodiment of the invention referring to the apparatuscomprises:

[0043] a pulse generating means for generating high voltage impulsesrequired for igniting spark discharge and producing energy sufficientfor fragmenting the calculus,

[0044] a probe for insertion within the body and transferring the energyto the calculus, said probe comprises a sheath with electrodes, whichreside within the sheath, said electrodes are provided with respectivedistal and proximal ends, the proximal ends of said electrodes areelectrically connected to the pulse generating means and the distal endof at least one of the electrodes is adapted to be in electrical contactimmediate with the calculus,

[0045] a probe manipulating means, for manipulating the sheath withinthe body and bringing at least one of the electrodes in electricalcontact with the calculus.

[0046] The present invention and its two main embodiments have only beensummarized briefly. For better understanding of the present invention aswell of its embodiments and advantages, reference will now be made tothe following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 shows schematically how spark discharge is initiated inelectro-hydraulic lithotriptor and electro-impulse lithotriptor.

[0048]FIG. 2 is schematic block diagram of an apparatus forelectro-impulse lithotripsy in accordance with the present invention.

[0049]FIG. 3 shows an embodiment of the pulse generator, employed in thelithotriptor of the present invention.

[0050]FIG. 4a shows another embodiment of the pulse generator, employedin the lithotriptor of the present invention

[0051]FIG. 4b is more detailed schematics of the pulse generator, shownin FIG. 4a.

[0052]FIG. 5 depicts control circuit employed with the pulse generator,shown in FIG. 4b.

[0053]FIGS. 6a-6 c show schematically principle of electro-hydraulic andelectro-impulse lithtripsy

[0054] FIGS. 7-10 refer to various embodiments of a probe, employed inthe lithotriptor of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0055] With reference to FIG. 1 the principle of operation ofelectro-hydraulic destruction and electro-impulse destruction can beexplained as follows.

[0056] A source 110 of high voltage impulses supplies the impulsesthrough a commutating means 120 to a working location 130, which isfilled up with a working fluid and where reside electrodes 140. Ignitingof spark discharge between the electrodes is used for destroying anobject 150, residing at the working location. It is not shownspecifically but should be understood that the object may comprise acalculus, which should be fragmented and the working location maycomprise a body cavity, where the calculus is located being surroundedby the body fluid, e.g. a gull stone appearing within the gall bladder,a stone within urinary system, etc.

[0057] The left picture (a) refers to the electro-hydraulic destructionand shows that since the electrodes are not in immediate contact withthe object its destruction is caused mainly due to shock waves SW causedby the spark discharge and propagating through the working liquidtowards the object.

[0058] The right picture (b) refers to the principle of electro-impulsedestruction and shows that the electrodes are placed immediate on theobject surface to locate the spark discharge within the bulk of theobject. Due to this provision the high voltage spark discharge producesspark channel within the object itself. Due to release of impulse energywithin the spark channel the pressure within the channel dramaticallyincreases, diameter of the channel enlarges causing tensile stresseswithin the object. The object is efficiently fragmented and destroyeddue to those tensile stresses in combination with hydraulic pressure ofthe surrounding liquid medium and collisions with the fragments of theobject. The present invention concerns intracorporeal lithotripsycarried out in accordance with the electro-impulse principle.

[0059] It has been revealed that the probability of propagation of thespark channel through the bulk of the object increases when the speed ofintroducing the energy within the object increases. Practically thismeans that it is advantageous to apply high voltage impulses defined byvery short rise time and duration. In practice it has been found thatfor fragmentation of wide assortment of calculi, appearing in a livingbody and requiring intracorporeal lithotripsy it is advantageous if theelectrical impulses supplied to electrodes are defined by the followingparameters: impulse rise time t_(f) less than 50 nanoseconds, preferablyless than 40 nanoseconds, duration of impulse itself t_(i) not more than5000 nanoseconds, preferably 500-3000 nanoseconds, impulse energyW₀=0.1-1.0 joule, impulse amplitude U=5-20 kV. The preferredconfiguration of the impulses is rectangular.

[0060] The pulses can be applied either as onetime impulses or asrepeating impulses with frequency of several Hz.

[0061] It has been also empirically found that by virtue of supplyingelectro-impulses with the above parameters it is possible to destroy acalculus, having electrical strength, which is more than the pulseamplitude, since the electrical breakdown threshold against repeatingimpulses, is lower than the electrical breakdown threshold against asingle impulse. At the same time, the energy spent for destruction ismuch less than the total energy of the supplied impulses, since all theimpulses except the last one are associated with partial discharge. Inpractice it is advantageous to supply to the electrodes high voltageimpulses with positive polarity, since this is associated with increasedbreakdown probability.

[0062] It has been found, that by virtue of the present invention thateven after applying of a single impulse or a few impulses it is possibleto destroy efficiently various calculi. It can be readily appreciatedthat the energy level, associated with the applied impulses is abouttwo, three and more times lower, than in the conventionalelectro-hydraulic lithotripsy and this is additional advantage of theinvention.

[0063] In FIG. 2 is shown schematically an apparatus 200 for carryingout the method of intracorporeal electro-impulse lithotripsy inaccordance with the present invention. The apparatus comprises a pulsegenerator 201, connected to a probe 203 and means 202 for manipulatingthe probe when it is inserted within the patient's body.

[0064] The pulse generator schematic comprises the following maincomponents: a charging means 210, an energy storage means (e.g. acapacitor) 220, a switching means 230, a pulse generating circuit 240and a control circuit 250. As suitable charging means one can use a DCvoltage or pulsed power supply and as suitable switching means one canuse known in the art spark-gap and control switches, e.g. transistors,thyristors, thyrotrones and other electronic switches. The particulardesign of the pulse generator can vary. For example, in accordance withone embodiment of the generator, which is shown in FIG. 3 and isdesignated by numeral 300 the generator comprises a transmission line310 made of coaxial cable, having fixed length, wave resistance Z andcapacity C_(p). This line is fed by a power source 320 up to a voltageU₀ in order to create positive wave of voltage and then to dischargethis voltage via a commutating means 330 to a load 340, havingresistance R_(H), for example a calculus. The specific feature of thisembodiment lies in that the beginning of the one of cable conductingwires is connected to its end and thus once the commutating means islocked the wave mode initiates simultaneously at both ends of the cable.Since the line is loaded at one of its ends with a resistance 360, whichis equal to wave resistance (R_(c)=Z) the reflections do not rise atthis end and there is no repeating impulses in the load 340 irrespectiveof its resistance R_(H). The pulse duration in the load is equal to thetime of wave propagation from one end of the line to the other. Theamplitude of voltage and current in this generator is defined by thefollowing relationships:

U=U ₀ R _(L)(Z+R _(L)) I=U ₀/(Z+R _(L)).

[0065] If R_(L)=Z, then U=0.5U₀ and l=U₀/2Z.

[0066] In this embodiment the impulse energy, which will be released onthe load R_(H) is two times less than the accumulated energy, since theload resistance R_(c) absorbs half of the energy.

[0067] If R_(L)>>Z the voltage impulse amplitude on the load approachesthe feed voltage U₀.

[0068] In practice a coaxial cable was used with wave resistance 50 om,specific capacity 0.1 nanofarad per meter and wave propagation speed 5nanoseconds per meter. If the cable has length 50 m then the pulseduration on the load is about 250 nanoseconds at a capacity C_(p)=5nanofarads. The accumulated energy, defined as W=C_(P)U²/2 varied from0.25 to 1 joule in accordance with the voltage variation from 10 to 20kV.

[0069] The pulse rise time on the load depends on the parameters of theswitching means. In practice it was about 15 nanoseconds. It has beenalso found, that if R_(c)>>Z it is possible to achieve flat top pulsewith duration of tenths of microseconds. The pulse will be terminated bya breakdown (short circuit) in the R_(L) or will descend exponentiallywith a time constant τ=C_(p)R_(L) if there is no breakdown.

[0070] Now with reference to FIG. 4a another embodiment of the pulsegenerator means will be discussed. In this embodiment the pulsegenerator 400 is designed as a “concentrated capacitance”. As in theprevious embodiments the pulse generator is connected to a probe 420,which is manipulated by a manipulation means 410.

[0071] In this embodiment the pulse generator schematic comprises acharging means 430, connected in parallel with a first capacitor 440,which in its turn is connected via a non-controllable switch 450 with aseparating inductivity 460, with a secondary capacitances 470,471,472,473 and with a transformer means, consisting of induction coils480,481,482,483 wound around common ferrite core (not shown). Theschematic comprises also a controllable switch 451, couple of currentsensors 490,491 and a control circuit 495, provided with a pulsecounter, indicator of pulse generation mode and indicator of breakdownmode. Sensor 490 resides in the first winding of the transforming meansand is used for counting the total amount of voltage pulses, generatedduring the treatment.

[0072] Sensor 491 resides in the second winding of the transformer meansand senses the occurrence of breakdown between the electrodes andestablishing of a spark channel. Both sensors are connected to thecontrol circuit, which controls operation of the charging means andterminates it as soon as either a preset amount of pulses has beengenerated or the breakdown occurs, whatever comes first.

[0073] Referring now to FIG. 4b the schematics of “concentratedcapacitance” embodiment will be explained in more details.

[0074] This schematics is designated by numeral 500 and comprises agroup of first stage capacitors C1, C2, a separating inductive coil L1,two discharge means P1 (non-controllable) and P2 (controllable), a groupof second stage capacitors C3-C6, a pulse transformer T3, elements R7,C7, P3 constituting a control circuit for discharge means P2, andinduction sensors T4, T5, connected in parallel with respectiveresistors R9, R8.

[0075] Sensor T4 senses the impulses in the first winding of the pulsetransformer T3, i.e. all the impulses delivered to the object. Sensor T5senses the impulses in the discharge winding of the pulse transformerT3. The sensor is adjusted to detect impulses, which cause the breakdownthrough the object. There is provided also a dedicated microcircuit,which will be explained later on, which passes the signal, correspondingto each impulse to a pulse counter (not shown) for counting thegenerated impulses. In practice the pulse sensor may be a Rogovski coilor any other type suitable sensor.

[0076] A high voltage rectifier charges the first stage capacitors bymeans of a circuit, consisting of a transformer T2 and diodes VD1, VD2,which are shunted by resistors R1-R4. The resistors limit the pulsecurrents through the transistors when capacitors C1, C2 discharge.

[0077] As soon as the voltage on the capacitors is sufficient for thebreakdown in the discharge means P1 the second stage capacitors arecharged via inductive coil L1. Each of the capacitors C3-C6 dischargeson the first winding of the pulse transformer T3 after the dischargemeans P2 has worked.

[0078] The amplitude and frequency of the impulses depends on theparticular position of the control switch S2 and on the discharge meansP1 and P2.

[0079] A control circuit 510 is provided, which is equipped, inter alia,with a relay K1 and light indicators VD3, VD4 and VD5, indicatingcorrespondingly “Net”, “Discharge” and “Breakdown”. The control circuitis connected to a pedal switch S3 for switching distantly the pulsegenerator from the mode “Discharge” to the mode “Stop”. The controlcircuit is connected via a transformer T1 and a switch S1 to a netsupplying voltage of 220 v and frequency 50 Hz.

[0080] The generator is switched on via contacts of relay K1, which isdistantly controlled by the pedal switch S3. Once the generator isswitched on the light indicator VD4 lights up and shows the mode“Discharge”.

[0081] Referring now to FIG. 5 it is shown a control circuit 510,comprising inter alia a pulse counter, consisting of microcircuits DA1,DA2, transistors VT1 and VT2, and a microcircuit DD1, which compares theamount of generated pulses with the preset value. Before switching onthe pulse counter is set to the required amount of working impulsesbetween 1 up to 99.

[0082] After the generator is switched on the generated pulses aresensed by sensor T4 and transistor VT2 passes the signals associatedwith those pulses to the pulse counter. As soon as the amount ofgenerated pulses reaches the preset value the microcircuit DD1 closestransistor VT1 and the generator is automatically switched off. Thefurther functioning of the generator is possible only after repeatedpushing down and release of the pedal switch S3.

[0083] Once a breakdown occurs and spark channel is established, thegeneration of impulses is terminated and light indicator VD5 lights upto announce this event. In this situation the pedal switch should bereleased to stop the generator. The calculus is observed in order todecide about the further treatment. If after observation it is found,that the calculus requires further fragmentation the generator isswitched on again by onetime pushing down and release the pedal switch,each time followed by observation the calculus.

[0084] The described above pulse generator is capable to generate pulseswith duration of about 1000 nanoseconds and with pulse rise time ofabout 50 nanoseconds and impulse amplitude in the range of 10-20 kV.

[0085] It can be readily appreciated that since the above describedcontrol circuit allows limiting the amount of pulses, which arepotentially harmful for the patient it is possible to carry out thetreatment more safely and at the same time more reliably.

[0086] The above-described generator employs energy storage means, whichcomprises capacitance. It should be understood, however, that it wouldbe possible also alternative storage means, for example comprisinginductive means.

[0087] In accordance with the invention one can contemplate variousmodes of electrical contact between the electrodes and the object.

[0088] With reference to FIG. 6 it is shown schematically various modesof spark discharge propagation depending on the disposition of theelectrodes with respect to the object to be fragmented. FIG. 6a refersto conventional electro-hydraulic destruction and shows schematically ahigh voltage central electrode 610, which is surrounded by a secondannular electrode 620, formed as a tubular member concentric with thefirst electrode. An object 630, e.g. a calculus is seen, which isdistant from both electrodes and due to a gap 640 none of the electrodesis in immediate electrical contact with the calculus. Shock waves 650produced by a spark discharge 660 propagate towards the calculus. Nodischarge channel is formed in the calculus.

[0089] In FIG. 6b is seen that both electrodes are brought in immediateelectrical contact with the calculus and there is no more gaptherebetween.

[0090] A discharge channel 660 originates between the electrodes withinthe bulk of the object and causes its destruction due to formation ofplurality of small cracks 670.

[0091] In FIG. 6c is seen how only the second electrode is brought inimmediate electrical contact with the object, while the centralelectrode is kept distant therefrom. Nevertheless, the discharge channelis still formed within the bulk of the object and causes itsdestruction. Now with reference to FIGS. 7 a-d it will be described theprobe for electro-impulse lithotripsy treatment, which enables immediateelectrical contact with the object to be fragmented in accordance withthe mode, shown in FIG. 6b.

[0092] The first embodiment of the probe is designated by numeral 700.In this embodiment the probe itself comprises a tubular sheath 710,through which extends a high voltage central electrode 711, electricallyinsulated from the interior of the sheath by an insulation covering 712.It is advantageous if the sheath 710 is made of dielectric material,however it might be made alternatively from electrically conductivematerial, covered by insulation coating. A second electrode 713 isprovided. This electrode comprises tubular member, which resides withinthe sheath coaxially and concentrically with the central electrode.

[0093] The distal extremity of the second electrode is provided with acouple of elastic contacts 714, which are electrically insulated by aninsulation coating 715. Both electrodes reside within the sheath withpossibility for their independent linear displacement along thelongitudinal axis of the probe from a fully retracted position, in whichthe electrodes are contained entirely within the sheath to a fullyprotracted position, in which the electrodes are outside the sheath.When in protracted position the electrodes can approach the outsidesurface of a calculus to be fragmented and then high voltage impulsescan be supplied to the electrodes from the pulse generator.

[0094] It is not shown specifically but should be realized, thatproximal extremities of the electrodes are operatively connected to amechanism for linear displacement, which is referred in FIGS. 2, 4a asprobe manipulating mean 202 and 410 respectively. It should beunderstood that the displacing mechanism might comprise any suitablemeans, conventionally used in lithotriptor devices for manipulating theprobe.

[0095] Also it is not specifically shown in FIG. 7a, that one of theelectrodes is electrically connected to the pulse generator to receivehigh voltage impulses with the above-described parameters and the otherelectrode is grounded.

[0096] In FIG. 7a is depicted the situation when both electrodes arestill in their retracted position within the sheath and are about toexit from the sheath.

[0097] In FIG. 7b is seen that the second electrode is brought in themost protracted position, in which its elastic contacts 714 approach astone 716 and are in immediate electrical contact therewith. The centralelectrode is still within the sheath and is ready to be protractedtowards the stone to establish electrical contact with it.

[0098] In accordance with the invention the amount and specificconfiguration of elastic contacts might be different. In practice thecontacts are made of biologically inert, elastic and electricallyconductive material, e.g. TiNi or any other suitable material, includingso called memory shape alloys. Insulating coating covers the contactsexcept of their tips, which should contact the stone.

[0099] In the embodiment shown in FIG. 7a the elastic contacts areprovided with rectilinear configuration and their tips are bent at anacute angle with respect to the longitudinal axis of the probe. Byvirtue of this provision it is possible to enable better grasping andcontainment of the stone and at the same time to ensure reliableelectrical contact with its surface.

[0100] In FIG. 7c is shown alternative embodiment of the probe in whichthe sheath is made of electrically conductive material and the secondelectrode is covered by an insulation coating 717. The distal extremityof the second electrode is provided with a couple of elastic contacts718, which have arcuate configuration. In FIG. 7d is shown still furtherembodiment in which the elastic contacts of the second electrodecomprise a retrieval basket 719 suitable for immobilization of the stoneand retaining thereof during the treatment. An example of such a basketis described in our previous patent application PCT/IL01/00591 hereinincorporated by reference.

[0101] Still another embodiment of the probe is shown in FIG. 7e. Inthis embodiment the sheath is made of metallic material and instead oftwo concentric electrodes a single symmetric cable 720 is used, which isplaced within the sheath with possibility for linear displacement alongthe sheath. The cable is provided with two conducting wirings 721,722,connected at their proximal ends to the pulse generator (not shown).Distal ends of the electrodes connected, e.g. by soldering to elasticcontacts 723, for example similar to those, which have been alreadymentioned. FIGS. 7e, f respectively show the probe provided with thetwo-wire cable when it is in protracted and retracted position.

[0102] Still further embodiment of the invention is shown in FIG. 7g, inwhich for supplying impulses two separate insulated wirings are usedinstead of a single symmetrical cable. These two insulated wirings maybe parallel one to another or twisted between them. As in the previousembodiment the elastic contacts are connected to the distal ends of bothwirings and their configuration is suitable for grasping the stone andestablishing immediate electrical contact therewith. In practice theelectro-impulse lithotriptor of the invention should be used incombination with an endoscope, equipped with suitable optics enablingmonitoring the procedure within the living body. The endoscope isintroduced in the body before the probe and is brought proximate to thecalculus. After that the probe is entered and brought near to thecalculus. Once the probe resides in the required position its electrodesare protracted from the probe by the displacement mechanism until theytouch the calculus. If the probe consists of two concentric electrodesthe second electrode, carrying the elastic contact is protracted firstand after that the central electrode. Once the calculus is grasped bythe contacts the pulse generator is switched on and voltage impulseswith the above-mentioned parameters are supplied to the electrodes toignite spark discharge, resulting in propagating of discharge channelthrough the bulk of the calculus, which results in destroying thecalculus.

[0103] Referring now to FIGS. 8a-c still further embodiments of theprobe will be explained. These embodiments are suitable for establishingelectrical contact with the object in accordance with the mode shown inFIG. 6c.

[0104] As in the previous embodiments a probe 800 is provided with ahigh voltage central electrode 810, extending along the probe andinsulated therefrom by a sleeve 811 made of a dielectric material, e.g.TEFLON or FEP or PTEE, or any other suitable material, which ismechanically resistant to shocks waves, developed during the treatment.

[0105] The forwardmost end of the central electrode is exposed to allowelectrical contact with the object to be destroyed (not shown) as soonas the electrode is brought in physical contact therewith. A secondelectrode 812 is provided, which has cylindrical shape and residesconcentrically with the central electrode. The second electrode iselectrically insulated from the interior of the probe by an insulationcovering 813 also made of a dielectric material. In contrast to theprevious embodiments the second electrode is not provided with elasticcontacts or basket or any other means, enabling gripping and containmentof the object. Instead of this to the forwardmost end of the secondelectrode is attached a washer 814, which is made of an electricallyconductive material. To the proximal extremity of the probe is attacheda mouthpiece member, having a cup-like forward portion 815 and askirt-like rear portion 816. The inside diameter of the forward portionexceeds the outside diameter of the probe and there is provided anannular space therebetween. A short bushing 817 made of electricallyconductive material resides in the annular space to enable electricalcontact with the second electrode via the washer. The length of thebushing and of the rear portion of the mouthpiece member are selected insuch a manner, that the forward most end of the central electrode andthe forward most end of the bushing lie in the same plane P andconstitute working electrodes. In practice it is required, that thelength of contact between the bushing residing within the mouthpiecemember and the probe is 4-6 mm. Once the probe is brought to the objectand working electrodes touch it an electrical contact can be establishedin accordance with the mode shown in FIG. 6b or FIG. 6c. It can bereadily appreciated, that by virtue of the embodiment shown in FIG. 8ait is possible to localize the spark channel at the very end of theprobe and thus to allow its propagation either through the surface ofthe object, or through its bulk, and thus to ensure much more efficientdestruction than in conventional electro hydraulic lithotripsy. Withreference to FIG. 8b still further embodiment of the probe is shown, inaccordance with which an auxiliary contact 818 made of resilientrefractory material is secured on the forwardmost end of the centralelectrode. Examples of suitable material for auxiliary contact compriseTiNi, stainless steel etc. Due to this contact the probability ofpropagation of the spark channel through the object improves and so theservice life of the probe. Still further embodiment of a probe providedwith a contact element made of electrically conductive super elasticmaterial (e.g. stainless steel) or of a shape memory alloy (e.g. NiTi)is shown schematically in FIGS. 9 a,b,c.

[0106] The probe is formed with a central electrode 901 electricallyinsulated by a coating 902 from a second electrode 903, which isparallel to the central electrode. The second electrode is displaceablealong the probe and to its forward most end is attached a loop-likecontact element 904, made of narrow strip or filament. This contactelement is capable to bend around the calculus when the second electrodeis in protracted position shown in FIG. 9b. The central electrode isalso displaceable along the probe and once it is brought in contact witha calculus 905 the contact element starts bending around the calculus asseen in FIG. 9c to allow the loop reliably contact with the calculus.The bending is possible either due to super elasticity of the loopitself or, when it is made of a memory shape alloy, by virtue of smallvoltage applied thereto.

[0107] Examples of a real probe, made in accordance with this embodimentare seen in FIGS. 10 a,b.

[0108] By virtue of the invention it is possible to fragment variouscalculi in the body more efficiently by applying energy, which isseveral times less, than in conventional electro-hydraulicintracorporeal lithotripsy. This becomes possible, since thefragmentation is caused by tensile stresses, caused by propagation ofthe spark channel, which goes through the surface or the bulk of thecalculus.

[0109] Furthermore, since the fragmentation can be carried outselectively by applying desired amount of impulses instead of pluralityof high frequency impulses the treatment is safer for the patient, andthe probability for traumatizing adjacent body tissues is less.

[0110] It can be also appreciated that since the amount of high voltageimpulses required for producing electrical breakdown between theelectrodes can be preset in advance, the contacts wear less and thus theprobe service life is longer.

[0111] The probe construction is simple and therefore reliable. Itallows grasping and containment of the calculi during the treatment andthis also contributes to the reliability of the treatment.

[0112] It should be understood that the present invention should not belimited to the above described example and embodiments. One ordinarilyskilled in the art can make changes and modifications without deviationfrom the scope of the invention. For example, as a sensor for sensingthe generated impulses one can use an inductive or capacitive sensor,instead of a current sensor for detecting the breakdown event one canuse an inductive sensor, or a capacitive sensor, or a resistive sensoretc.

[0113] The specification referring to FIG. 4b does not disclose indetails the particulars of various components shown, e.g. diodes,resistances, integrated circuits, since selecting of these particularslies within routine work, required from one skilled in the art.

[0114] It should be appreciated that the features disclosed in theforegoing description, and/or in the following claims, and/or in theaccompanying drawings may, both separately and in any combinationthereof, be material for realizing the present invention in diverseforms thereof.

What is claimed is:
 1. A method for fragmenting of various calculi in aliving body by intracorporeal lithotripsy treatment, during which aprobe is brought to the calculus to be fragmented, said probe isprovided with electrodes, connected to a means for generating of highvoltage impulses, said impulses are supplied to the electrodes forigniting spark discharge between them and release of energy, causingfragmenting of the calculus, wherein the method comprises bringing of atleast one of the electrodes in electrical contact immediate with thecalculus so as to establish a discharge channel capable to create shockwaves and stresses, which excess the strength of the calculus material.2. The method of claim 1, in which said high voltage impulses aredefined by the following parameters: impulse rise time t_(f) less than50 nanoseconds, duration of impulse itself t_(i) not more than 5000nanoseconds, impulse energy W₀=0.1-1.0 joule, impulse amplitude U=5-20kV
 3. The method as defined by claim 2, in which said impulses aresupplied as single impulses.
 4. The method of claim 2, in which saidimpulses are supplied as repeating impulses with frequency of up toseveral tens of Hz.
 5. The method of claim 2, in which said impulses aredefined by the following parameters: impulse rise time t_(f) less than40 nanoseconds, duration of impulse itself t_(i) not more than 3000nanoseconds.
 6. The method of claim 5, in which the amplitude of saidimpulses, is below the value of single pulse breakdown threshold of thecalculus.
 7. The method of claim 1, comprising sensing the onset of theelectrical breakdown, associated with fragmenting of the calculus. 8.The method of claim 7, comprising termination of the generation of thehigh voltage impulses as soon as the onset of the electrical breakdownis sensed.
 9. The method of claim 8, comprising presetting certainamount of high voltage impulses to be supplied to the electrodes,counting the amount of impulses actually generated by the generator andtermination the generation as soon as either the preset amount isachieved or the electrical breakdown is sensed.
 10. The method of claim1, comprising grasping the calculus before supplying the impulses andits containment during supplying the impulses.
 11. An apparatus forfragmenting of calculi within a living body during intracorporeallithotripsy treatment, said apparatus comprising: a pulse generatingmeans for generating high voltage impulses required for ignitingelectrical breakdown and producing energy sufficient for fragmenting thecalculus, a probe for insertion within the body and transferring theenergy to the calculus, said probe comprises a sheath with electrodes,which reside within the sheath, said electrodes are provided withrespective distal and proximal ends, the proximal ends of saidelectrodes are electrically connected to the pulse generating means andthe distal end of at least one of the electrodes is adapted to be inelectrical contact immediate with the calculus, a probe manipulatingmeans, for manipulating the sheath within the body and bringing at leastone of the electrodes in electrical contact with the calculus.
 12. Theapparatus of claim 11, in which said electrodes comprise a firstelectrode, which extends along the longitudinal axis of the sheath and asecond electrode, which is concentric and coaxial with the firstelectrode, said electrodes are electrically insulated, except of theirforwardmost ends, which are intended to be in electrical contact withthe calculus.
 13. The apparatus of claim 11, in which the electrodesreside within the sheath with possibility for their linear displacementalong the sheath from a retracted position to a protracted position andthe distal ends of the electrodes are adapted to be in electricalcontact immediate with the calculus when at least one of the electrodesis brought in the protracted position,
 14. The apparatus of claim 13, inwhich said electrodes comprise a first electrode, which extends alongthe longitudinal axis of the sheath and a second electrode, which isconcentric and coaxial with the first electrode, wherein the distal endof the second electrode is connected to a spreadable contacts, adaptedto be opened and to grasp the calculus when the second electrode is inthe protracted position.
 15. The apparatus of claim 14, in which saidspreadable contacts are made of elastic, electrically conductivematerial, said contacts are electrically insulated, except of theirforwardmost ends, which are intended to be in electrical contact withthe calculus.
 16. The apparatus of claim 14, in which the contacts aremade of TiNi.
 17. The apparatus of claim 15, in which the contacts haverectilinear configuration and their most forward ends are bent.
 18. Theapparatus of claim 15, in which the contacts are provided with archedconfiguration.
 19. The apparatus of claim 15, in which the contactscomprise a retrieval basket.
 20. The apparatus of claim 12, in which theelectrodes comprise two conducting wires extending along a cable. 21.The apparatus of claim 12, in which said pulse generating meanscomprises a charging means, a first capacitor means, a commutatingmeans, a pulse generating circuit and a control circuit.